Information handling systems have used diverse formats for recording data on peripheral data recorders. When a given data recording format has been selected, the programming of the information handling system is designed to operate with the selected format. This limitation means that data recorders have to use the format contemplated in the programming, and vice versa. Some emulation of one recording format on another recording format has been achieved; such emulation has not enabled the programming to easily address the emulated format. That is, emulation software had to translate the addresses of the first format into different addresses of the second format. Such address translation not only obscures the record addresses of the first format when recorded over the second format but also can require substantial buffering and instruction execution resources.
Marilyn Bohl in INTRODUCTION TO IBM DIRECT ACCESS STORAGE DEVICES, publication SR20-4738, Science Research Associates, Inc. Chicago, Ill., in Chapter 4 describes two data formats. The first is the well known count, key, data (CKD) format used on International Business Machines Co. (IBM) disk recorders, also termed disk files and DASDs. Many large scale information handling systems employ CKD data format in their programming and recording. Bohl also describes fixed block (FB) recording, also termed fixed block architecture (FBA) format.
The CKD format enables efficient usage of disk space for large records by dividing disk track recording format in accordance with record size, whereas the FBA format uses a set of identically-sized addressable areas (termed blocks), each of which can store up to some fixed amount of data, such as 512 bytes, 1024 bytes, 2048 bytes, etc. For small record sizes (such as less than 512 bytes) FBA may have some advantages over CKD. In any event, information handling systems are employed which have DASDs some of which use CKD while others use FBA formats. Many of the programs executed in the systems are designed to work with CKD format; therefore it is desired to enable CKD formatted data to be recorded on record disks or members in FBA devices. It is also desired to maintain the CKD record addressability for all data records stored in FBA formats.